Treatment of hydrocarbons in plural stages to produce lower boiling hydrocarbons



Nov. 21, 1967 c. H. BRODEUR ETA. 3,354,075

TREAIMENT OF HYDROCARBONS IN PLURAL STAGE TO PRODUCE LOWER BOILING HYDROCARBONS Filed Dec. 29, 1965 United States Patent O 3,354,075 TREATMENT OF HYDROCARBONS IN PLU- RAL STAGES T `PRODUCE LOWER BOIL- ING HYDRCARBONS Charles H. Brodeur, Beacon, N.Y., and Warren G. Schlinger, Pasadena, Calif., assignors to Texaco Inc., New York, NX., a corporation of Delaware Filed Dec. 29, 1965, Ser. No. 517,390 9 Claims. (Cl. 20S- 58) This invention relates to the treatment of hydrocarbons. More particularly, this invention is concerned with the conversion of heavy hydrocarbon liquids having high carbon and/or metal contents into lighter hydrocarbon liquids of reduced carbon and/or metal content in the presence of hydrogen.

The hydrocarbonliquids to which the process of this invention may be applied generally have a wide boiling range and may contain materials ranging from naphtha through kerosene, gas oil, tar and asphalt. Suitable starting materials include the various whole crudes and heavy fractions thereof such as Arabian crude or San Ardo crude, or depending on the type of products desired, topped or reduced crude. If it is desired to produce large amounts of gaseous hydrocarbons, the feed ordinarily will include naphtha. If it is desired to produce large amounts of motor lfuel, the feed will be composed primarily of hydrocarbon boiling above the naphtha range. Practically, there is no 4upper limit on the boiling range of the feed stock.

Several methods for the hydroconversion of heavy hydrocarbons into lighter hydrocarbons are known. In one particularly advantageous process for the conversion of hydrocarbon oils, the hydrocarbon oil, in intimate mixture with hydrogen, is/passed throu-gh a tubular reaction zone at elevated temperature and pressure under conditions of highly turbulent ow. The effluent from the tubular reaction zone is then introduced into a separation zone wherein the gaseous material is separated from material which is liquid at the prevailing conditions. The separated liquid material, at substantially the same temperature and pressure, is contacted with a separately heated stream of hydrogen. Some additional hydroconversion takes place in the contacting zone with the formation of hydrocarbons vaporous at the prevailing conditions. Removal of entrained or dissolved gaseous material from the separated liquid is also effected in the contacting zone and the resulting gaseous stream comprising unreacted hydrogen'and vaporous hydrocarbon is combined with the gaseous material separated from the tubular reaction zone eluent. The combined stream is -then passed into contact With a hydrogenation catalyst. Such a process is disclosed in U.S. patent application Ser. No. 33,582, filed June 2, 1960, now U.S. Patent No. 3,089,843 of which one of us is co-inventor.

The bottoms removed from the contacting zone are tar-like in nature in that they have a hi-gh carbon residue, a high pour point and high viscosity. The tarry bottoms usually also have high sulfur and nitrogen contents. ln addition essentially all of the metals present in the feed are concentrated in the bottoms. In many instances, delpending on the feed and/ or operating conditions this material is solid at room temperature.

Because of the tar-like nature of the contacting zone bottoms, it was not considered advisable to subject this material to further treatment to upgrade it into desirable liquid products. Ordinarily, heavy hydrocarbon materials may be upgraded -as Iby thermal cracking or coking. Such procedures are not too satisfactory however as the products for the most part are coke and fixed gases and the yield of liquid products is relatively small. In the case of the bottoms from the contacting zone even 3,354,075 Patented Nov. 2l, 1967 ICC such treatment was not considered practical because of the tar-like nature of this material. It was believed from past experience that subjecting this tarry material to conventional treatment would produce large amounts of coke with negligible yields of -middle distillates. Accordingly, it was considered that the most expedient method of utilizing this bottoms product was to add thereto a light cutter oil to reduce its viscosity thereby producing a pumpable mixture for use as a fuel of the Bunker C type.

The present invention has for an object the conversion of tarry material such as that obtained from the process described above into good yields of lighter hydrocarbons. Another object of the invention is to convert such heavy hydrocarbons into metal-free cracking stocks of reduced sulfur and nitrogen contents. Various other objects will be obvious to those skilled in the art from the following disclosure.

The process of the present invention has particular iapplication in the treatment of hydrocarbon liquids containing residual components, metals and other tarand ash-forming constituents. Hydrocarbon liquids to which the process of the present invention is particularly adapted are those having Conradson carbon values of at least about 1% by weight. Examples of charge stocks to which the process of the invention may be applied success-fully are crude oils such as Santa Maria crude, Sau Ardo crude, Arabian crude, Venezuelan crude, Safaniya crude and heavy fractions of crude oils such as reduced or topped crude, deasphalted oil, vacuum residuum and mixtures thereof Iand the like. Other materials which may be advantageously treated yare coal oil, pitches, tars, gilsonite, shale oil and tar sand oil.

The hydrogen employed in the process of the present invention may be substantially pure, e.g. l-99% by volume or may be dilute hydrogen such as a gas mixture containing -as little as 40% by volume hydrogen obtained for example by the partial combustion of carbonaceous fuels. Suitable sources of hydrogen are catalytic reformer hydrogen, electrolytic hydrogen or synthesis gas which last may be used as produced or which may be used after being subjected to a Water gas shift conversion land then scrubbed for CO2 removal. The term hydrogen as used in the present specification and appended claims includes not only pure hydrogen but also includes dilute hydrogen. Preferably, the gas referred to as hydrogen contains at least about 65 volume percent hydrogen and, to prevent excessive hydrogen consumption, is substantially free of CO and CO2.

The hydrogen and hydrocarbon pass through the tubular reaction zone under such conditions of temperature, pressure and turbulence that the reactants are in the form of an intimate mixture. The turbulence level, that is the ratio of the average apparent viscosity to the kinematic viscosity, should be at least 25. In actual practice, experience has shown that the turbulence level is usually much greater, generally in excess of 100. Under these conditions the oil or at least that portion which remains liquid under the reaction conditions is in the form of tine mist-like droplets suspended in a gaseous medium comprising hydrogen. Under these conditions, the hydrogen is in close proximity to cracked fragments Which are formed during the hydroconversion so that the unsaturated cracked fragments can react with the hydrogen in preference to inter-reacting to form large hydrocarbon molecules.

The hydrocarbon feed and the hydrogen are introduced at elevated temperature and pressure into a tubular reaction zone through which the reactant stream is passed under conditions of highly turbulent ow. Ordinarily the temperature in the tubular reaction zone is maintained between about 700 and 1,000 F., preferably between 800 and 950 F. Pressure inthe reaction zone is advantageously maintained between about 500 and 5,000 p.s.i.g. Economically satisfactory results are obtained when the outlet pressure of the tubular reaction zone is between about 1,000 and 2,000 p.s.i.g. A stoichiometric excess of hydrogen is circulated. Hydrogen circulation rates of between about 4,000 and 95,000 s.c.f.b. (standard cubic feet per barrel) of fresh feed are used, at least 1000 s.c.f.b. being supplied to the oil-hydrogen reactor and at least 3000 s.c.f.b. being supplied to the contacting zone as described more fully below. Preferred rates range between 6,000 and 15,000 s.c.f.b.

The effluent from the tubular reaction zone, in the form of nely-divided oil droplets suspended in a vaporous medium comprising hydrogen and vaporous hydrocarbons, is passed into a separation Zone wherein the gaseous materials comprising hydrogen and vaporous hydrocarbons are separated from the liquid materials. The separated liquid material is composed for the most part of tar-like material relatively rich in hydrogen from which entrained or dissolved lighter hydrocarbon material is removed by contacting the separated liquid material with a gaseous stream comprising hot hydrogen.

In the process of the present invention, after the liquid material has been contacted with hydrogen preferably in a countercurrent manner, the separated tar-like residue or a portion thereof is sent to a second reaction zone which is maintained at substantially the same temperature and pressure as the tubular reaction zone. Advantageously, the temperature in the second reaction zone is slightly lower than the temperature in the tubular reaction zone and the residence time of the heavy hydrocarbon material in the second reaction Zone, if desired, may be Vlonger than in the tubular reaction zone. The reaction in the second reaction zone is carried out in the absence of added hydrogen.

Preferably the second reaction zone is elongated or tubular in form and the heavy hydrocarbon material passes therethrough under conditions of turbulent iiow. This additional treatment serves to convert the heavy hydrocarbon material into good yields of middle distillates without forming excessive amounts of coke despite the fact that no hydrogen is added with the feed to the second reaction zone.

The eiiluent from the second reaction zone is composed of a gaseous portion comprising vaporous hydrocarbons and a liquid portion comprising unvaporized hydrocarbons. The gaseous portion is combined with the gaseous portion of the effluent from the tubular reaction zone and the liquid portion is combined with the liquid portion of the effluent from the tubular reaction Zone. The combined liquid portion or a portion thereof, after hydrogen contacting, is then recycled to the second reaction Zone through which it is passed in the absence of added hydrogen. Advantageously a portion of the combined liquid is Withdrawn from the system to prevent the build up of metals.

The combining of the respective gaseous and liquid streams can be effected in several ways. For example, the effluents from the tubular reaction Zone and the second reaction zone may be combined and a single separation made of the combined effluents into a gaseous stream and a liquid stream. The liquid stream can be contacted with hot hydrogen and the unconverted residue sent to the second reaction zone. The hot contacting hydrogen and vaporous hydrocarbons contained therein may be then added to the gaseous stream.

It is also possible to separate the effluents from each reaction zone into their respective gaseous and vaporous streams and then combine the streams. For example, the effluent from the tubular reaction zone may be introduced into the upper section of a tower, the effluent from the second reaction zone may be introduced into the intermediate section of the tower and hot hydrogen is introduced into the lower section of the tower. In this case, the hydrogen is introduced into the lower section of the tower at a rate between about 3,000 and 90,000 s.c.f. preferably between 6,000 and 50,000 s.c.f. per barrel of fresh feed to the tubular reaction zone. The effluent from the tubular reaction zone is separated into a gaseous portion and a liquid portion which latter descends through the tower. This liquid portion in its descent through the tower comes in contact rst'with rising vaporous hydrocarbons separating from the elliuent from the second reaction zone, combines with the liquid portion of the eiuent from the second reaction and the combined liquid stream comes into contact with the hydrogen introduced into the bottom of the tower. The hot hydrogen, rising through the tower, contacts the combined liquid stream of the effluents from the tubular and the second reaction zones, combines with the gaseous portion of the eiiluent from the second reaction zone and this combined hydrogen and vaporous hydrocarbon stream leaves the upper portion of the tower with the gaseous portion of the effluent from the tubular reaction zone.

Alternatively, the effluent from the tubular reaction zone may be introduced into the lower section of the tower and the effluent from the second reaction zone introduced into the tower at a point spaced above the point of entry of the effluent from the tubular reaction zone. The effluent from the tubular reaction zone is separated into a gaseous phase comprising hydrogenand vaporous hydrocarbons which rises through the tower coming into contact with the liquid portion of the effluent from the second reaction zone. The rising stream is combined with the vaporous portion of the effluent from the second reaction zone and leaves the tower by means of an outlet in the upper section thereof. The liquid portion of the effluent from the second reaction zone descends through the tower, combines with the liquid portion of the eiiiuent from the tubular reaction zone and the combined stream or a portion thereof is recycled to the second reaction zone through which it is passed in the absence of added hydrogen.

Advantageously the combined gaseous stream while still hot is passed into Contact with a hydrogenation catalyst under hydrogenation conditions, after which the reactant stream may be separated into a gas rich in hydro gen, which is recycled, and into various hydrocarbon frac tions which may be used as such or may be subjected to additional treatment.

Suitable hydrogenation catalysts comprise the oxides and/ or suliides of cobalt, nickel, chromium, manganese, vanadium or molybdenum used alone or in combination with each other or with other compounds such as suliides or oxides of tungsten. The catalysts may be supported on a base such as silica, alumina, ymagnesia, or mixtures thereof.

The amount of catalyst in the vhydrogenation zone is suicient to provide a space velocity of between 0.1 and l0 volumes of normally liquid hydrocarbon per volume of catalyst per hour. Preferably the amount of catalyst will provide a space velocity of between 0.75 and 3 v./v./ hr. Hydrogen rates in the catalyst zone are determined by the amount of hydrogen introduced into the tubular reaction zone and the contacting zone depending on hydrogen consumption in the earlier steps will range upwards from about 4,000 cubic feet per barrel of hydrocarbon liquid introduced into the initial tubular reaction zone. Preferably, the reactant stream is cooled to a temperature below about 850 F. for example, 725-800 F. prior to its introduction into the catalytic zone.

For a better understanding of the invention reference is now made to the accompanying drawing which shows diagrammatically a iiow scheme for the practice of the present invention.

Hydrocarbon oil feed together with recycle hydrogen from line 31 and make-up hydrogen from line 12 is introduced through line 11 to oil-hydrogen heater 14 which is in the form of a tubular reaction zone and through which the reactant stream is passed under conditions of highly turbulent How. Euent from oil-hydrogen heater '14 is introduced into the upper section of tower 17 gaseous portion which leaves tower 17 through line 20 and a liquid portion which descends through tower 17. During its descent through the tower the liquid portion is countercurrently contacted with vaporous hydrocarbons separated from a hydrocarbon mixture introduced into tower 17 through line 21. In its further descent, the liquid portion is combined with the liquid portion of the hydrocarbon mixture `introduced through line 21 and this combined stream is then countercurrently contacted with hot hydrogen introduced into the lower section of tower 17 through line 23. The combined liquid stream after contact with the hot hydrogen is removed from tower 17 through line 25 and is transferred to tar reactor 27 through line 26. A portion of the tarry liquid is removed from the system through Iline 28.

Alternatively the eluent from oil hydrogen heater 14 may be introduced into the lower section of tower 17 by means of line 16, 38 and 23. In the lower section of tower 17 eflluent from line 23 is separated into a gaseous por- `tion comprising hydrogen and vaporous hydrocarbons and a liquid portion. The gaseous portion rises through tower 17, countercurrently contacting the descending liquid portion of the hydrocarbon mixture introduced through line 21, and combining with the vaporous portion of the hydrocarbon mixture introduced through line 21. This combined gaseous and vaporous mixture leaves tower 17 through line 20 and the combined liquid portions are withdrawn from tower 17 through line 25 and recycled to tar reactor 27 through line 26. When elluent from oilhydrogen heater 14 is introduced into the lower section of tower 17 through lines 16, 38 and 23, it is possible to reduce or in some cases dispense with hydrogen introduced from heater 40 thereby reducing to a large extent the amount of hydrogen circulated throughout the system.

The combined gaseous and vaporous portions are cooled by means of .a heat exchanger or other means (not shown) and introduced into catalyst chamber 39 which contains a hydrogenation catalyst. Although flow through catalyst chamber 30 is indicated to be downow, the reactants alternatively may be passed upwardly through catalyst chamber 30. Product stream is removed through line 32 and introduced into high pressure separator 33 from which a gas rich in hydrogen is separated and recycled through line 31 a portion being sent through line 36 to hydrogen heater 40 and a separate portion through line 11 to oil-hydrogen reactor 14. Liquid from high pressure separator 33 is then passed through line 34 to a fractionation zone represented by column 40 from which various fractions such as normally gaseous hydrocarbons, naphtha and middle distillates may be removed through lines 41, 42 and 43, respectively.

If desired, eluent from tar reactor 27 may be introduced into the upper section of tower 17 by means of lines 21, 19 and 16.

In Run 1 of the following example, the feed, a San Ardo crude, with hydrogen is passed through the oilhydrogen lreactor and the etiluent is introduced into the upper section of a tower where it is separated into a gaseous portion and a liquid portion. Separately heated hydrogen is introduced into the lower section of the tower and countercurrently contacts the descending stream of liquid. After the contacting, the liquid is withdrawn from the bottom of the tower and the hydrogen together with vaporous materials removed or formed during the contacting is combined with the gaseous portion of the eiiluent and the combined stream is subjected to catalytic hydrogenation. Run 2 is similar to Run 1 except that a portion of the liquid withdrawn from the bottom of the tower, amounting to 14.8% by volume basis feed is removed from the system and the balance sent to the tar reactor, the effluent of which is introduced into the intermediate section ofthe tower.

The following data show thesuperior yields of desirable products obtainable by the procedure'of vRun 2.

Feed:

Gravity, API Viscosity, S81? at 210 F Run 1 Run 2 Reaction Conditions:

Oil-hydrogen reactor outlet, F 890 890 Tar reactor outlet, F 850 Hydrogen heater outlet, F- 900 Tower pressure, p.s.i.g 1, 635 Catalyst chamber inlet, F.- 773 Catalyst chamber outlet, F y 800 800 Hydrogen to oil-hydrogen reactor s.c.f.b. basis fresh feed 8,300 8, 500 Hydrogen to hydrogen heater, s.c.f.b. basis fresh feed 12, 5,00 12, 400 Hydrogen consumption, s.c'.f.b 580 770 Product Yield:

Oil yield, vol. percent basis fresh feed 79.1 88. 0 Tar yield, vol. percent basis fresh feed 22. 3 14.5 Product Oil:

Gravity, API l 28. 4 Viscosity SSu/122 F 1 43. 4 Su fur, wt. percent 0.24 Nitrogen, wt. percent 0.32 Distil1ation,

IBP 210 10%- 408 50% 604 Product Tar:

Gravity, API 0. 9 -5. 1 Carbon residue, wt. percent.. 37. 0 40. 1 Sulfur, wt. percent- 1.96 1. 88 Nitrogen, wt. percent- 1. 40 1. 65 Carbon, wt. percent 86. 5 88.1 Hydrogen, wt percent 9.2 8.3 Nickel, p.p.m 252 334 Vanadium, p.p.m 380 396 We claim:

1. A process for the hydroconversion of a hydrocarbon liquid which comprises passing said hydrocarbon liquid in the presence of between about 1,000 and 100,000 s.c.f. of hydrogen -per barrel of said hydrocarbon -liquid through a tubular reaction zone under conditions of turbulent flow at a temperature between about 750 and 950 F. and a pressure between about 500 and 20,000 p.s.i.g. for a residence time between about 5 and 100 seconds, removing from said tubular reaction zone a lirst elfluent containing a gaseous phase comprising hydrogen and vaporous hydrocarbons and a liquid phase comprising unvaporized hydrocarbons, stripping said liquid phase with hot hydrogen, passing at least a portion of said stripped liquid phase to a second reaction zone maintained at a temperature between about 700 and 950 F. and a pressure between about 500 and 20,000 p.s.i.g. for a residence time between about 5 and 100 seconds, the temperature in said second reaction zone being lower than the temperature in the tubular reaction zone, removing from said second reaction zone a second effluent containing a gaseous phase comprising vaporous hydrocarbons and a liquid phase comprising unvaporized hydrocarbons and combining the liquid phases of said rst and second eiiiuents the sole reactant feed to said second reaction zone being liquid material recovered from the stripping step.

2. The process of claim 1 in which the gaseous phases from said first and second eiuents are combined and the resulting combined stream is contacted with a hydrogenation catalyst under hydrogenation conditions.

3. The process of claim 2 in which the catalyst comprises molybdenum.

4. The process of claim 3 in which the catalyst comprises compounds of molybdenum and nickel.

5. The process of claim 3 in which the catalyst comprises compounds of molybdenum and cobalt.

6. The process of claim 1 in which the temperature in said second reaction zone is lower and the residence time in said second reaction zone is longer than the tern`x perature and residence time respectively in the tubular reaction zone, the eliuent from said tubular reaction zone is combined with the effluent from the second reaction zone, the combined eluents are separated into a gaseous portion comprising hydrogen and Vaporous hydrocarbons and a liquid portion comprising unvaporized hydrocarbons, said liquid portion is contacted with a stream of hydrogen separately heated to a temperature between about 700 and 950 F. to remove dissolved and entrained vaporous hydrocarbons from said liquid portion and the separately heated hydrogen stream containing removed vaporous hydrocarbons is combined with said gaseous portion.

7. The process of claim 1 including the steps of separating said rst efuent from said tubular reaction zone into a rst gaseous stream comprising hydrogen and vaporous hydrocarbons and a first liquid stream comprising unvaporized hydrocarbons, countercurrently contacting said first liquid stream with a mixture of hydrogen and vaporous hydrocarbons obtained as described below, passing at least a portion of said contacted rst liquid stream to a second reaction zone maintained at a temperature between about 700 and 950 F. and a pressure between about 500 and 20,000 p.s.i.g. for a residence time between about 5 and 100 seconds, the temperature in said second reaction zone being lower and the residence time in said second reaction zone being longer respectively than the temperature and residence time in said tubular reaction Zone, contacting the effluent from said second reaction zone with a stream of hydrogen separately heated to a temperature between about 700 and 950 F. to remove dissolved and entrained vaporous hydrocarbons from the liquid portion of the eluent from said second reaction Zone and contacting the first liquid stream with the separately heated hydrogen stream containing removed vaporous hydrocarbons.

8. The process of claim 7 in which an inert gas is added to said irst liquid stream prior to its introduction into the second reaction zone.

9. The process of claim 7 including the steps of separating the eliiuent from the second reaction zone into a second gaseous stream comprising vaporous hydrocarbons and a second liquid stream comprising unvaporous hydrocarbons, countercurrently contacting said second liquid stream with said first gaseous portion and passing the resulting gaseous stream into contact with a hydrogenation catalyst under hydrogenation conditions.

References Cited UNITED STATES PATENTS 5/1963 Eastman et al 208-58 9/1964 Tulleners 208-56 

1. A PROCESS FOR THE HYDROCONVERSION OF A HYDROCARBON LIQUID WHICH COMPRISES PASSING SAID HYDROCARBON LIQUID IN THE PRESENCE OF BETWEEN ABOUT 1,000 AND 100,000 S.C.F. OF HYDROGEN PER BARREL OF SAID HYDROCARBON LIQUID THROUGH A TUBULAR REACTION ZONE UNDER CONDITIONS OF TURBULENT FLOW AT A TEMPERATURE BETWEEN ABOUT 750 AND 950*F. AND A PRESSURE BETWEEN ABOUT 500 AND 20,000 P.S.I.G. FOR A RESIDENCE TIME BETWEEN ABOUT 5 AND 100 SECONDS, REMOVING FROM SAID TUBULAR REACTION ZONE A FIRST EFFLUENT CONTAINING A GASEOUS PHASE COMPRISING HYDROGEN AND VAPOROUS HYDROCARBONS AND A LIQUID PHASE COMPRISING UNVAPORIZED HYDROCARBONS, STRIPPING SAID LIQUID PHASE WITH HOT HYDROGEN, PASSING AT LEAST A PORTION OF SAID STRIPPED LIQUID PHASE TO A SECOND REACTION ZONE MAINTAINED AT A TEMPERATURE BETWEEN ABOUT 700 AND 950*F. 